Fluorescent tubes are widely used in a variety of locations such as schools and office buildings for providing area lighting, for example. A fluorescent tube typically produces an even distribution of light about its circumference. However, the circumferentially uniform light produced by typical fluorescent tubes may be modified after exiting the tube such that the light distribution becomes directional with a greater amount of light directed in a first radial direction compared to a second radial direction.
Consider the example of a fluorescent light fixture installed in a ceiling. The light produced by a fluorescent tube installed in such a fixture is typically intended to illuminate an area below the ceiling. A reflector is often positioned above the fluorescent tube to redirect upward traveling light toward the area below the ceiling to be illuminated. The reflector can in effect increase the efficiency of the fluorescent tube by redirecting light that would otherwise illuminate an area where illumination provides limited or no benefit, such as a portion of the ceiling above the fluorescent tube in the present example, toward an area where illumination provides a greater benefit. Reflectors used to make light produced by fluorescent tubes directional are present in many existing fluorescent tube fixtures.
LED-based light tubes have been developed for use in fluorescent light fixtures to replace conventional fluorescent tubes. LED-based light tubes, by definition, each include one or more LEDs. LEDs output light directionally, typically in a Lambertian distribution. A typical LED-based tube is constructed with its LEDs arranged to face in a common direction. As such, the typical LED-based tube should be installed in a fixture in a specific orientation, specifically with its LED oriented to produce light toward an area to be illuminated. For example, when installed in a fixture in a ceiling that has a reflector as described above, the typical LED-based tube is installed to be oriented such that its LEDs face away from the reflector. Due to the orientation of the typical LED-based tube and the directional output of the typical LED-based tube when installed in the ceiling fixture, a large portion of produced light travels directly toward an area below the ceiling that is intended to be illuminated, and thus a typical LED-based tube produces minimal amounts of light in the direction toward the reflector. As a result, the reflectors attached to many fluorescent light fixtures serve little purpose when typical LED-based tubes are installed in the fixtures.